In terms of instrumental goals ('keep society functioning'), I think these are secondary concerns. A person might believe that we are all in a perpetual state of decay; a doctor finds it necessary to understand the kidneys of a high-functioning adult so that later problems may be diagnosed and fixed. Even if decay itself might take a long time- and even if decay is ultimately inevitable- there are reasons to want to understand and replicate the rules that provide access to 'doing okay, for now'.

Departing from my steelman for a moment, I think a more pressing concern with the model might be a poor understanding of the environmental pressures on specific societies. Homeostasis is contextual- gills are a bad organ for somebody like me to have. In the case of human societies, it's not obvious what these environmental pressures might be, or what consequences they might have. Technology is certainly one of them, as are other human societies, as are material resources and so on, but it's just not a well constrained problem. Does internet access alter the most stable implementations of copyright law? Does cheap birth control change the most economically viable praxis of women's education? Would we expect Mars colonization to result from a new cold war? So I think it is not enough to show that a society endured- you have to show that the organs of that society act as solutions to currently existing problems, otherwise they are likely to multiply our miseries.

(Rejoinder to the rejoinder: Chesterton's Fence.)